I don't think it doubles thier research, what I think the biggest effect of the bonus is, is that it lets them break out of some expansion plateau they get caught in. For example, if you play games with the ability to view all scores and watch the AI, you'll see that they hit this plateau where they just stop getting any more resources and research for a long, long time. They also dramatically slow down thier planetary colonization. After a while, they pick up again, but by then, any human is way ahead of them. Most of the AI's seem to hit this with between 15k and 40k research. If you put on the low bonus, they will not hit this plateau, but will be able to continue expanding straight through the game. And that, I believe, is what accounts for their much higer research. I think the actual bonus is much closer to the 10% guesed at below.
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